Apparatus such as transistors are known. Transistors such as graphene field effect transistors may be used as sensors. For example the transistors may be configured to act as photo-sensors, X-ray sensors, infrared sensors bio-sensors, chemical sensors or any other suitable types of sensors.
Such apparatus are often required to be small enough to fit into other electronic devices such as communication devices. In some examples the transistors may be provided on semiconductor wafers or dies. It is useful to have reliable methods of providing such small scale apparatus.